1. Field of the Invention
The present invention relates to a zoom lens system. Moreover, the present invention relates to an electronic image pickup apparatus in which the zoom lens system is used.
2. Description of the Related Art
In recent years, replacing a silver-salt film camera, a digital camera in which, an object is photographed by using a solid image pickup element such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor) has become a mainstream. Furthermore, there are several categories of digital cameras in a wide range from a high-function type for professional use to a compact popular type.
A user of the popular type digital camera seeks to enjoy photography readily, anywhere at any time with a wide range of scenes. In light of this, a small size product particularly a slim digital camera which can be accommodated easily in a pocket of clothes or a bag, and carried conveniently has been preferred.
On the other hand, while a magnification ratio of about 3 for a digital camera of a compact type has been common, a camera of a magnification ratio higher than a magnification ratio of the conventional one has been sought. As a zoom lens system which is capable of maintaining easily a comparatively higher magnification ratio, a zoom lens system having in order from an object side, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, and a third lens unit having a positive refracting power has hitherto been known.
On the other hand, in a size of the camera, a size in a direction of thickness of a camera is determined mainly by a size of a lens barrel. Therefore, for achieving slimming of a camera, slimming of the lens barrel is effective.
Nowadays, a so-called collapsible barrel which is pushed out from an inside of a camera body when the camera is in use, and is accommodated inside the camera body while carrying the camera has been common. Therefore, a zoom lens system in which slimming of the lens barrel when collapsed has been sought.
In conventional technologies in Japanese Patent Application Laid-open Publication Nos. 2005-242116, 2005-326743, and 2006-78979, a zoom lens system in which a first lens unit includes two or three lenses, and an aberration correction and a reduction in size of a second lens unit is carried out by making a symmetrical power arrangement in the second lens unit, by arranging in order from the object side, a negative lens, a positive lens, and a negative lens, has been disclosed.